Light and/or High Compactness fabric, in Particular for Parachutes

ABSTRACT

The invention relates to a fabric made of continuous warp yarns and weft yarns, comprising 30 to 63 warp yarns and 30 to 63 weft yarns per centimetre, and in which the yarns are spread so as to lie in a same plane, the yarns having a dtex of between 11 and 78 dtex and a DPF (decitex per filament) defined in the following manner on the basis of the number of warp and weft yarns: (I) the fabric has a weight of between 27 and 40 g/m2 and a perviousness to air lower than or equal to 120 l/m2/s at 127 Pa, as measured according to the ASTM-D-737 standard (1 hour) on a measuring surface of 20 cm2. AA BB Nombre de Nombre de fils de DPF (dtex) fils de chaîne trame 1.0 ≰ DPF ≰ 1.35 30-49 30-49 1.35 &lt; DPF ≰ 2.3 35-63 35-63 AA Number of warp yarns BB Number of weft yarn.

The present invention relates to fabrics having improved properties notably of lightness and/or compactness, which are of great interest for making articles such as parachutes. The object of the invention is also a method for making such a fabric as well as articles such as parachutes, made from this fabric.

Traditionally, the parachute consists of a harness bag which contains a main jump canopy and an emergency (or reserve) canopy.

The parachute webbing should meet a certain number of technical criteria such as tear resistance, lifetime, porosity. Parachute manufacturers have technical know-how allowing them to meet the specifications for the main canopy and the emergency canopy.

Traditionally, the manufacturing involves the use of synthetic or natural yarns consisting of a multitude of continuous filaments. These yarns are interlaced according to traditional weaving techniques. The thereby obtained so-called <<raw>> fabric is then cleaned in order to suppress the products for protecting and lubricating the yarns, notably the sizing, but different steps are conducted with the purpose of making the properties of the fabric more homogeneous over the whole of its surface. One of the main functional properties of the fabrics is perviousness to air. It is this property which will allow the fall to be slowed down, main function of the parachute.

Parachutes are often built with a nylon fabric of the rip-stop type. Rip-stop nylon is a fabric with square meshing, with warp and weft yarns positioned at 90° with respect to each other, certain yarns are doubled, tripled or more generally in a regular way.

Depending on the required air perviousness (permeability) level, the fabric may be heat-set (a heat treatment for stabilizing the properties), dressed (deposition of a chemical dressing giving particular properties), calendered (having the fabric pass under pressure between heated cylinders), coated (deposition of a polymer layer).

For coated fabrics, the material is typically calendered, and then coated with a material based on silicone or other polymer. The silicone material or other material allows the pores of the fabric to be filled in order to adjust the porosity and therefore control the perviousness and the behavior of the canopy.

The principle is always the same, the larger the apparent surface area of the yarns, the more they will perturb and therefore slow down the air flow. Treatments, coating and dressings increase this apparent surface area.

Two properties are today very much sought after in the world of parachuting. The first of these properties is the compactness of the fabric with which it is possible to obtain a folded volume as reduced as possible in order to limit the bulkiness of the harness bag containing the jump canopy and the emergency canopy. The other one of these properties is lightness for quite obvious reasons.

For an identical surface area, low compactness is generally easier to obtain for the emergency canopy which is generally a canopy made from a non-coated fabric having low porosity. These properties are more difficult to obtain for the main jump canopy which is generally made in a coated fabric so as to have very low porosity, so-called zero porosity. The major difficulty for increasing lightness and/or compactness, is to have the fabric retain properties allowing it to be always suitable to its use in the making of parachute canopies. The same problem exists in other applications such as paragliding canopies, kites for kite surfing, sails of sailing boats, notably spinnakers or gennakers.

The present invention aims at improving the compactness level and/or the lightness of these fabrics, notably those which may be used for making parachute canopies.

The object of the present invention is therefore a fabric formed with continuous warp yarns and continuous weft yarns, comprising from 30 to 63 warp yarns and from 30 to 63 weft yarns, per cm, and in which the filaments are spread out so as to appear in the same plane, the yarns have a titer comprised between 11 and 78 dtex and a DPF (decitex per filament) defined in the following way, according to the number of warp and weft yarns:

DPF (dtex) Number of warp yarns Number of weft yarns 1.0 ≦ DPF ≦ 1.35 30-49 30-49 1.35 < DPF ≦ 2.3 35-63 35-63

The spreading of the filaments in a same plane is a significant characteristic of the invention. With this spreading it is possible to place the warp, respectively weft filaments so that they are parallel with each other or substantially parallel. Notably because of the meshing and therefore of the crossing and of the superposition of the yarns at the yarn crossings, the spreading out of the filaments in a same plane may not be perfect, however the use of very fine filaments gives the possibility of obtaining optimized spreading. By spreading in a same plane, the invention therefore also covers spreading substantially in a same plane.

The fabrics according to the invention are therefore characterized by the use of yarns comprising a large and optimized number of constitutive filaments. The spreading of these filaments is facilitated. Further, for a same fabric weight, the surface area which is then covered is greater than what is obtained traditionally with yarns including a more restricted number of filaments with a larger diameter. The weight/surface ratio is also optimized, notably because the thickness of the fabric is reduced by the spreading out of finer filaments. The invention defines an optimum between the weight of the fabric, the number of yarns per cm and the filamentary spreading. The compactness of the fabric is also optimized, whether this be at the centre or at the fold, by the synergistic combination of the use of finer filaments and of spreading of the filaments. The fabrics according to the invention may be used as such, for example for making the emergency canopy of a parachute, or after coating for example for the main jump canopy of the parachute. The invention then provides again another advantage. The optimum spreading of the filaments ensures that for a given fabric weight and a given number of yarns per cm, the spaces between constitutive yarns of the fabric are reduced as much as possible and the coating payload rate is reduced, which allows reduction in the amount of coating and therefore in the weight of coated fabric. This also allows optimum compactness to be preserved after coating.

The constitutive yarns of the fabric according to the invention are preferably yarns with parallel filaments.

The fabric according to the invention is advantageously a fabric with square meshing, with warp and weft yarns crossed at about 90°. According to a preferred embodiment, this is a rip-stop fabric.

The constitutive material of the filaments is preferably a synthetic or artificial material. This may notably be polyamide, polyester or viscose.

In a preferred embodiment, this is polyamide notably polyamide 6.6 (PA 6.6, Nylon 6.6).

In an embodiment, the yarns have a titer comprised between 22 and 44 dtex, preferably between 33 and 44 dtex.

According to an advantageous characteristic, the yarns have a tenacity greater than or equal to 5.8 cN/dtex preferably greater than or equal to 6 cN/dtex, for example between 5.8 and 7, or 6 and 7 cN/dtex.

In a particular embodiment, the number of warp yarns and of the weft yarns is comprised between 30 and 62, notably between 30 and 60.

In two other embodiments, the fabric fits the following characteristics:

DPF (dtex) Number of warp yarns Number of weft yarns 1.0 ≦ DPF ≦ 1.35 37-47 37-47 1.35 < DPF ≦ 2.3 40-59 40-59

According to an embodiment, this fabric is also coated, notably in order to obtain very low porosity. By very low porosity, is meant in the sense of the invention, a porosity or air perviousness of less than or equal to 1 L/m²/s under 1,000 Pa, as measured according to the ASTM D-737 standard (1 hour) over a measuring surface area of 20 cm². Such a fabric may advantageously be used for a main jump canopy.

According to another embodiment, the fabric meets the following characteristics:

Number of yarns (for the warp and for the weft) DPF (dtex) 35-49 1.0 ≦ DPF ≦ 1.35 50-63 1.35 < DPF ≦ 2.3

The fabric meeting this definition may be used as such with low porosity. By low porosity is meant in the sense of the invention, a porosity or air perviousness of less than or equal to 15 L/m²/s under 127 Pa, as measured according to the ASTM D-737 standard (1 hour) over a measuring surface area of 20 cm². Such a non-coated fabric may advantageously be used for an emergency canopy.

According to another embodiment, the fabric meets the following characteristics:

Number of yarns (for the warp and for the weft) DPF (dtex) 30-45 1.0 ≦ DPF ≦ 1.35 35-47 1.35 < DPF ≦ 2.3

The fabric meeting this definition may be used as such or coated. If non-coated, its porosity or air perviousness may be less than or equal to 120 L/m²/s under 127 Pa, as measured according to the ASTM D-737 standard (1 hour) over a measuring surface area of 20 cm². Such a non-coated fabric may advantageously be used for an emergency canopy.

The compactness of a fabric may be measured at the overlap of several fabric thicknesses (a so-called measurement at the centre) and at the fold. The measurement at the centre gives information on the compactness obtained by stacking several fabric thicknesses. It is not sufficient per se. The measurement at the fold is more informative since it gives access to the foldability of the fabric, and to the overall compactness of a fabric folded several times on itself, as in the case of a parachute canopy folded in the harness bag. According to the invention, the measurement at the centre is a measurement of the thickness of 12 superposed fabric layers. The measurement at the fold is the value of the maximum thickness at the <<flattened>> fold joining 12 layers of fabric. The fabric sample to be characterized is deposited around two fingers borne by a supporting plate. The controlled rotation of this plate allows superposition of 12 fabric layers in a reproducible way. One finger is then retracted, which releases the folded fabric from any tension and the latter is deposited on a measurement table or plate. A third finger is connected to means for measuring the thickness of material located between the finger and the measuring table or plate, these means give the possibility of measuring the thickness variations all along the measuring area. For the measurements, it is preferably the fabric which is moved with the plate under the finger, the latter being parallel to the fold. The value at the fold is the maximum thickness value recorded in the area of the fold during the passing of the finger over this area.

According to an embodiment, the fabric has a compactness of the fold of less than or equal to 0.65 mm, in particular less than or equal to 0.58 mm, preferably less than or equal to 0.52 mm. According to this embodiment, the fabric notably has compactness at the centre of less than or equal to 0.55 mm, in particular less than or equal to 0.52 mm, preferably less than or equal to 0.45 mm.

According to other characteristics, this fabric may have one, several or all the following characteristics:

-   -   a weight comprised between 27 and 40, preferably between 27 and         35 g/m²;     -   a thickness at the centre comprised between 36 and 45 μm;     -   air perviousness of less than or equal to 120, preferably less         than or equal to 15 L/m²/s under 127 Pa, as measured according         to the ASTM D-737 standard (1 hour) over a measuring surface         area of 20 cm².

According to an embodiment of the invention, the fabric is coated. It is coated on one face or on both of its faces. It is preferably coated on both of its faces, for example for parachute applications.

Preferably, this fabric includes a number of yarns (for the warp and for the weft) comprised between 37 and 47 and a DPF such that 1.0≦DPF≦1.35.

Advantageously, the coated fabric has a compactness of the fold of less than 0.85 mm, in particular less than 0.75 mm, preferably less than 0.65 mm.

Its compactness at the centre may notably be less than or equal to 0.75 mm, preferably less than or equal to 0.55 mm.

Its weight is advantageously comprised between 30 and 50, preferably between 30 and 40 g/m².

Advantageously, the coated fabric has a thickness comprised between 60 and 85 μm.

The coated fabric preferably has an air perviousness of less than or equal to 2, preferably 1 L/m²/s under a 1,000 Pa, as measured as according to the ASTM D-737 standard (1 hour) on a measuring surface area of 20 cm².

The coating may be carried out with materials currently used for coating fabrics used in applications of the parachute, paragliding, spinnaker, kite surf type, etc. These materials once they are polymerized or cross-linked have properties of adherence to the fabric and of elasticity suitable for these applications. Among the preferred materials, mention will be made of silicone materials.

Advantageously, the provision of coating material is optimized and may notably be such that the coating weight is reduced by about 25% with respect to the standard for similar porosity, this result being obtained as explained supra by the spreading of the filaments. For example a coating weight is comprised between 4 and 7 g/m², notably between 5 and 6 g/m².

According to a characteristic of the invention, the constitutive filaments of the yarns have a diameter comprised between 10 and 22 μm, preferably between 10 and 19.5 μm.

The spreading of the filaments may be carried out by any means. In the case when a coating is provided, the spreading precedes the coating. The spreading is carried out preferably on a fabric without any sizing and advantageously heat-set in the usual way.

According to an embodiment, the fabric is cleaned in order to remove the sizing, it is then heat-set, and then spreading is carried out.

Preferably, the spreading is carried out by calendering. The efficiency of calendering or of any other spreading procedure may easily be monitored by digital, electronic or optical microscopy with a suitable magnification. This allows one skilled in the art to adjust the spreading parameters depending on the fabric, in order to obtain optimum spreading, expressed by the fact that the filaments are substantially in the same plane.

For non-coated fabric, the calendering may be carried out in the presence of a sliding agent. For a coated fabric, this is not necessary.

According to a particular embodiment, the fabric notably in PA, preferably PA 6.6 is of the type with 46±1 warp yarns/cm, 46±1 weft yarns/cm, 26±1 filaments per yarn, yarns of 33±2 dtex, i.e. a DPF of about 1.27 dtex, heat-set, dressed and calendered. Fabric weight 33±1 g/m². See the properties in Example 2.

According to another particular embodiment, the fabric notably in PA, preferably PA 6.6 is of the type with 45±1 warp yarn/cm, 45±1 weft yarns/cm, 26±1 filaments per yarn, yarns of 33±2 dtex, i.e. a DPF of about 1.27 dtex, heat-set, calendered and coated (silicone coating weight of about 6-7 g/m²). Coated fabric weight is of about 39-40±1 g/m². See the properties in Example 2.

According to an advantageous characteristic, the fabrics of the invention have a tear strength greater than or equal to 1.5 daN according to the ISO 4674 test standard, or greater than or equal to 1.8 daN according to the ISO 13937-2 standard.

In an embodiment, an anti-sliding agent is applied on at least one portion of the surface of the yarns or on the fabric. This agent is notably applied on the assembling areas between two fabric pieces, for example on the areas for assembling by sewing. This anti-sliding agent may be formed with particles of a mineral nature, notably silica for example colloidal silica, fumed silica or diatomaceous silica. The particles preferably have a cross-section or an average diameter comprised between 5 and 100 nm. This anti-sliding agent may also be of an organic nature, for example based on an acrylic material. The anti-sliding agent may be present in an amount between 0.01 and 0.5%, preferably between 0.01 and 0.1% by weight based on a total weight of the fabric.

The fabrics according to the invention may find application in all the applications where a gain in compactness has an advantage. As a first field, mention may be made of applications for which reduced bulkiness is a determining advantage, which is notably the case of parachutes of large surface area and/or of parachutes loaded on board or used under conditions where the space which may be assigned to them is limited. As another field, mention may be made of applications for which it is advantageous to be able to increase the surface area of the fabric for identical bulkiness, for example for increasing safety or reducing the fall rate.

The fabrics according to the invention find an application in the field of parachuting, whether this is for parachuting persons or parachuting equipment, for example jettisoning equipment, in the civil or military field or further in an emergency or slowing-down parachute for a light aircraft for example (micro-light aircraft, drones, light airplane, etc.). They may find use more generally in various sports related to wind or air. Thus, the object of the invention is also a parachute canopy, a paragliding canopy, a kite surf kite, a sailing boat sail, notably a spinnaker or a gennaker or any other article comprising or formed with a fabric according to the invention.

The object of the invention is also a parachute bag, or a harness bag for parachuting, comprising at least one canopy comprising or formed with a fabric according to the invention, the canopy being the emergency canopy, preferably non-coated, or the main canopy, preferably coated. Preferably, this article contains both canopies comprising or formed with a fabric according to the invention.

The object of the invention is also the method for making such a fabric, wherein, after weaving the warp and weft yarns, preferably at 90°, notably in a rip-stop format, the filaments are spread out so that they appear substantially in the same plane. The spreading out may be carried out as described above, notably by calendering, under conditions notably defined above.

For non-coated fabric, the fabric may be heat-set and/or dressed, according to the methods and with the products usually used, before spreading.

For coated fabric, the spreading out is advantageously preceded with heat-setting. The spreading precedes the coating. The coating may be accomplished on one face or on both faces.

Heat-setting is a standard step, which may notably be conducted at a temperature comprised between 150 and 170° C.

The calendering is carried out at a temperature which may be comprised between 190 and 210° C. for the non-coated fabric and between 140 and 160° C. for the coated fabric.

The spreading, preferably calendering steps and optionally other steps such as heat-setting and application of a dressing, and coating, are preferably carried out after cleaning the so-called <<raw>> fabric, i.e. fabric from weaving. This cleaning aims at notably removing the sizing.

The invention will now be described in more detail by means of embodiments taken as non-limiting examples.

EXAMPLES Example 1

Two fabrics A an B in polyamide 6.6 are made, having the following specifications. Fabric C (comparative) is a standard fabric in PA 6.6 coated with silicone for a parachute. The weight of the fabric is measured according to BSEN 12127 and expressed in g/m².

A B C Linear weight of the warp/weft yarn (dtex) 22/22 22/22 33/35 Number of filaments per yarn 14 14 10 Number of warp yarns per cm 63 58 53 Number of weft yarns per cm 63 59 52 DPF (dtex) 1.58 1.58 About 3.4 Weight of the fabric (g/m²) 32 36 48

The fabric A is dressed and heat-set and then calendered. Fabric B is heat-set and then calendered and then coated with a silicone coating identical with that of fabric C.

The compactness measurements of 12 fabric layers are conducted as described supra and the obtained results are the following:

A B C Compactness at the centre (mm) 0.41 0.52 0.88 Compactness at the fold (mm) 0.47 0.68 1.11

The air perviousness was measured as described supra, under 127 Pa for A and under 1,000 Pa for B:

A B Air perviousness (L/m²/s) <15 <1

Example 2

Two fabrics D and E in polyamide 6.6 are made having the following specifications. The comparative fabric C is the same as in Example 1.

D E C Linear weight of the warp/weft yarn (dtex) 33/33 33/33 33/33 Number of filaments per yarn 26 26 10 Number of warp yarns per cm 46 45 52 Number of weft yarns per cm 46 45 52 DPF (dtex) 1.27 1.27 About 3.4 Weight of the fabric (g/m²) 33 39 48

The fabric C is dressed and heat-set and then calendered. The fabric E is heat-set and then calendered and then coated with a silicone coating identical with that of fabric C.

The compactness measurements of 12 fabric layers are conducted as described supra and the obtained results are the following:

D E C Compactness at the centre (mm) 0.5 0.78 0.88 Compactness at the folds (mm) 0.56 0.75 1.11

The air perviousness was measured as described supra, under 127 Pa for D and under 1,000 Pa for E:

D E Air perviousness (L/m²/s) <15 <0.05 

1. A fabric for a parachute canopy, a paragliding canopy or a sailing boat sail, formed with continuous warp yarns and weft yarns, comprising from 30 to 63 warp yarns and from 30 to 63 weft yarns, per cm, and wherein the filaments are spread out so as to appear in the same plane, the yarns have a dtex comprised between 11 and 78 dtex and a DPF (dtex per filament) is defined in the following way, depending on the number of warp and weft yarns: Number of warp Number of weft DPF (dtex) yarns yarns 1.0 ≦ DPF ≦ 1.35 30-49 30-49 1.35 < DPF ≦ 2.3 35-63 35-63

the fabric has a weight comprised between 27 and 40 g/m² and an air perviousness of less than or equal to 120 L/m²/s under 127 Pa, as measured as according to the ASTM D-737 standard (1 hour) on a measuring surface area of 20 cm².
 2. The fabric according to claim 1, characterized by the following characteristics: DPF (dtex) Number of warp yarns Number of weft yarns 1.0 ≦ DPF ≦ 1.35 37-47 37-47 1.35 < DPF ≦ 2.3 40-59 40-59


3. The fabric according to claim 1, characterized by the following characteristics: Number of yarns (for the warp and for the weft) DPF (dtex) 35-49 1.0 ≦ DPF ≦ 1.35 30-45 1.0 ≦ DPF ≦ 1.35 50-63 1.35 < DPF ≦ 2.3 35-47 1.35 < DPF ≦ 2.3


4. The fabric according to claim 1, characterized in that the fabric has a compactness of the fold of less than or equal to 0.65 mm, in particular less than or equal to 0.58 mm, preferably less than or equal to 0.52 mm.
 5. The fabric according to claim 1, characterized in that the fabric has a compactness at the centre of less than or equal to 0.55 mm, in particular less than 0.52 mm, preferably less than or equal to 0.45 mm.
 6. The fabric according to claim 1, characterized in that the fabric has a weight comprised between 27 and 35 g/m².
 7. The fabric according to claim 1, characterized in that the fabric has a thickness comprised between 36 and 45 μm.
 8. The fabric according to claim 1, characterized in that the fabric has an air perviousness of less than or equal to 15 L/m²/s under 127 Pa, as measured according to the ASTM-D-737 standard (1 hour) on a measuring surface area of 20 cm².
 9. The fabric according to claim 1, characterized in that the fabric is coated.
 10. The fabric according to claim 9, characterized by a number of yarns (for the warp and for the weft) comprised between 37 and 47 and a DPF such that 1.0≦DPF≦1.35.
 11. The fabric according to claim 9, characterized in that the fabric has a compactness of the fold of less than 0.85 mm, in particular less than 0.75 mm, preferably less than 0.65 mm.
 12. The fabric according to claim 9, characterized in that the fabric has a compaction at the centre of less than or equal to 0.75 mm, preferably less than or equal to 0.55 mm.
 13. The fabric according to claim 9, characterized in that the coated fabric has a weight comprised between 30 and 50, preferably between 30 and 40 g/m².
 14. The fabric according to claim 9, characterized in that the coated fabric has a thickness comprised between 60 and 85 μm.
 15. The fabric according to claim 9, characterized in that the coated fabric has an air perviousness of less than or equal to 2 L/m²/s under 1,000 Pa, as measured according to the ASTM-D-737 standard (1 hour) on a measuring surface area of 20 cm².
 16. The fabric according to claim 9, characterized in that the fabric is coated with a silicone material.
 17. The fabric according to claim 1, characterized in that the diameter of the filaments is comprised between 10 and 22 μm, preferably between 10 and 19.5 μm.
 18. The fabric according to claim 1, characterized in that the yarns are flattened by calendering.
 19. The fabric according to claim 1, characterized in that the yarns have a tenacity greater than or equal to 5.8 cN/dtex.
 20. The fabric according to claim 1, characterized in that it has a tear resistance greater than or equal to 1.5 daN according to the ISO 4674 test standard, or greater than or equal to 1.8 daN according to the ISO 13937-2 standard.
 21. The fabric according to claim 1, characterized in that an anti-sliding agent is applied on at least one portion of the surface of the yarns or of the fabric.
 22. A parachute canopy, a paragliding canopy or a sailing boat sail, comprising or formed with a fabric according to claim
 1. 23. A method for making a fabric according to claim 1, wherein after weaving the warp and weft yarns, the filaments are spread out so that they appear substantially in the same plane. 